Carriage and drive arrangement for cheese vats and curd tables

ABSTRACT

A carriage for driving an agitator or pusher moves on an elongated, vat mounted track and has three wheel engagement with the track. The take-off for the agitator drive or the pusher connection is made over the side of the track and the track is completely closed. The track and carriage are laterally offset relative to the center of the vat and the take-off and pusher connection are located generally on the vat center. A chain extending the length of the track is connected at both ends to the track and passes over a motor driven sprocket located in the carriage to move the carriage along the track. Two guide wheels are located between an angle bracket and one side wall of the track and move between that bracket and wall generally in alignment with the chain. One end of the chain is anchored by means of a spring to maintain a taut chain and is associated with a limit switch arrangement for interrupting the carriage drive in response to an overload on the pusher or agitator.

ilnite' States Patent Thomson [4 1 May 29, 1973 [75] Inventor: Meridith C. Thomson, Oconomowoc, Wis.

[73] Assignee: Stoelting Brothers Company, Kiel,

Wis.

[22] Filed: Mar. 2, 1971 [21] Appl. No.: 120,259

[52] [1.8. CI ..3l/47 Primary ExaminerHugh R. Chamblee Attorney-John W. Michael, Gerrit D. Foster. Bayard H. Michael, Paul R. Puerner, Joseph A. Gemignani, Robert E. Clemency, Andrew 0. Piteris, Glenn A. Buse and Spencer B. Michael [57] ABSTRACT A carriage for driving an agitator or pusher moves on an elongated, vat mounted track and has three wheel engagement with the track. The take-off for the agitator drive or the pusher connection is made over the side of the track and the track is completely closed. The track and carriage are laterally offset relative to the center of the vat and the take-off and pusher connection are located generally on the vat center. A chain extending the length of the track is connected at both ends to the track and passes over a motor driven sprocket located in the carriage to move the carriage along the track, Two guide wheels are located between an angle bracket and one side wall of the track and move between that bracket and wall generally in alignment with the chain. One end of the chain is anchored by means of a spring to maintain a taut chain and is associated with a limit switch arrangement for interrupting the carriage drive in response to an overload on the pusher or agitator.

18 Claims, 3 Drawing Figures CARRIAGE AND DRIVE ARRANGEMENT FOR CHEESE VATS AND CURD TABLES BACKGROUND OF INVENTION SUMMARY OF INVENTION This invention is primarily concerned with such over the side carriage arrangements and has among its principal objects the provision of an improved carriage support and/or drive arrangement.

For the achievement of these and other objects, this invention contemplates a carriage having three wheel support engagement with a track. The three support wheels will maintain continuous engagement with level as well as uneven surfaces and thereby insure a stable support for the carriage. The carriage is guided in its movement along the track by guide wheels positioned between opposed walls, the spacing between the walls being accurately controlled to insure proper tracking of the carriage. These features provide a stable and effective carriage which is suitable to an over the side arrangement.

Preferably, the carriage is driven along the track by means of an elongated element connected to the track and reeved over a drive element in the carriage. Movement of the drive element moves the carriage along the elongated element and on the track. This simplified arrangement provides a positive driving force for the carriage.

One end of the elongated element can be anchored relative to the track through a spring which holds the elongated element taut and against which the elongated element pulls should there be an increase in load on the pusher, or agitator, and consequently on the carriage. Movement of the elongated element against the spring can be used to control carriage movement and prevent unduly loading the carriage and/or pusher or agitator. For example, a limit switch can be associated with the elongated element to shut down the carriage drive should element movement exceed a preselected limit therebyindicating excessive loading.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the single embodiment shown in the drawings in which:

FIG. 1 is a section through a cheese vat and curd pusher combination;

FIG. 2 is a section view 2-2 of FlG. l; and

FIG. 3 is a generally schematic view in perspective of the carriage drive arrangement.

DESCRIPTION OF PREFERRED EMBODIMENT With particular reference to the drawings, the invention has been illustrated as embodied in a cheesemaktaken generally along line ing vat with a curd pusher connected to a carriage. The vat 10 is of generally conventional construction having inner and outer walls 12 and 14 separated by insulating media 16. The cheese-making equipment can be provided with a curd pusher 18 as illustrated in FIG. 1 or can be provided with a conventional rotating mechanical agitator. The function of the illustrated pusher and the alternative and mechanical agitator is well known and they can have a conventional, well known construction and therefore will not be described in detail.

Whether the pusher or an agitator is used, it is common practice to move that operative member through the cheese, curd, or whatever other media is contained in the vat. To accomplish this, that operative member is suspended from carriage 20 which is in turn supported by track 22. Thetrack is preferably a reinforced structural member so that it does not require hanger or ceiling attachments for support but can be connected directly to the vat. As illustrated, the track is mounted on the vat by means of two vertical posts 24 located one at each of the opposite ends of the vat, only one post has been illustrated in the drawing. Track 22 is supported directly above the vat and extends between the ends of the vat, i.e. generally the length of the vat but can stop short or extend beyond the vat ends.

The track as illustrated is elongated to conform to the elongate configuration of the vat. Also, the track is generally channel-shaped having a bottom 26 and upstanding side walls 28 and 30. As discussed in the aforementioned US. patent, all of the drive elements of the car riage, i.e. that for moving the carriage along track 22 and for rotating the mechanical agitator where one is used, are located above track 22. The bottom of track 22 is completely closed as are side walls 28 and 30 for sanitation reasons. The track being completely closed, any oil or foreign matter which might otherwise drip from the drive mechanism in the carriage cannot fall into the vat. This construction and the resultant sanitary nature thereof is possible due to the over the side connection of the operative member, i.e. the pusher or mechanical agitator, to the carriage as will be described more completely hereinafter.

Carriage 20 includes an outer housing 32 and a drive arrangement located within that housing. The drive arrangement will be described more completely hereinafter in connection with FIG. 3. Carriage 20 includes a portion which overhangs side wall 30 of the track, i.e. it extends laterally beyond that side of the track. The take-ofi- 34 to the pusher l8 (and the take-off to the mechanical agitator where that is used) is located in this overhang portion of the carriage. As can be seen in FIG. 1, track 22 is offset from the longitudinal center of vat 10 and the take-oilto pusher 18 is located generally on the center of the vat to position the pusher on the vat center. The same would be true of the mechanical agitator.

The support for carriage 20 on track 22 is provided by three support wheels 36, 38, and 40 visible in FIG. 2. These support wheels are mounted on horizontal axles 42, 44, and 46 which are in turn supported from brackets 48, 50, 52 connected to housing 32 of the carriage. The three wheel support for the carriage provides an effective and stable support for the carriage. The three wheel engagement with the track will maintain continuous engagement of all three support wheels with the track bottom whether the track bottom is level or somewhat uneven. As can be seen in FIG. 2, in a horizontal sense (i.e. projected to a horizontal plane) the three wheels 36, 38, and 40 upon which carriage 20 is supported are spaced triangularly. Preferably, the two support wheels 36 and 38 are located along side wall 30 which is adjacent to the take-ofi to the operative member in the vat. The third support wheel 40 is positioned at the opposite side wall, 28, and is positioned equal distance between wheels 36 and 38 relative to the longitudinal axis of the track.

A guide arrangement is also provided to insure proper tracking of the carriage along track 22. This guide arrangement consists of guide wheels 54 and 56 supported on vertical axles 58 and 60 which are in turn connected to brackets 62 and 64. Brackets 62 and 64 are each connected to a bracket 66 and 68 which are in turn connected to brackets 48 and 50 and to the housing 32 of the carriage. Because of the lengths in volved in the processing vat, and consequently in the track which is usually coextensive with that vat, it is difficult to maintain a true linear side wall along which to track guide members such as wheels 54 and 56. To insure proper tracking of carriage 20, this invention proposes to locate guide wheel 54 and 56 between opposed vertical walls which have a preselected spacing therebetween which spacing closely approximates the diameter of the wheels. Therefore, the wheels closely fit between the opposed walls and will cause the carriage to track well.

More specifically, as illustrated the inner side of upstanding side wall 30 of track 32 provides one of the opposed walls. An elongated angle bracket 70 is welded, or otherwise suitably attached, to the bottom 26 of the track. The upstanding leg 72 of the bracket provides the other wall between which wheels 54 and 56 are held. With this arrangement, brackets 70 can be accurately located relative to side wall 30 to maintain a uniform spacing between the side wall and leg 72 of the bracket to insure proper tracking of the carriage. For simplicity in construction, the guide wheels are provided on the same side of the carriage as the two support wheels 36 and 38 so that they can use the same basic attachment bracket for connection to the carriage.

The drive arrangement for propelling carriage 20 along track 22 consists of an elongated element, a chain 74. The chain is attached to track 22 so as to be generally stationary in the track. The chain is reeved over two idler sprockets 76 and 78, both supported from housing 32 by bracket 80. The chain proceeds from sprockets 76 and 78 to a driven sprocket 82 inside of carriage 20, see FIG. 3. Driven sprocket 82 is powered through gear reducer 84 by an electric motor 86. The connection between the gear reducer and the electric motor is made by belt 88. Accordingly, when sprocket 82 is driven it moves along chain 74 and consequently the carriage is propelled along track 22. The motor is reversible so as to drive the carriage, and correspondingly the pusher or mechanical agitator, in both directions through vat 10.

Preferably, one end of chain 74 has a fixed connection with respect to track 22. The opposite end is connected to the track by means of the'arrangement illustrated in FIG. 2. More specifically, chain 74 is connected to a swivel 90. A shorter portion of chain 92 is also connected to the swivel but is turned 90 from the chain orientation of chain 74. The shorter chain 92 is reeved onto and fixed to sprocket 94 which is supported from the tack on vertical axle 96. A lever 98 is fixed to sprocket 94. Compression spring 100 is seated between the end 102 of track 22 and lever 98. Spring 100 biases lever 98, and consequently sprocket 94, in a clockwise direction is viewed in FIG. 2. This biasing force tends to maintain chain 74 in a taut condition. It will be noted that spring 100 is supported on bolt 104 which also acts as a guide for the movement of lever 98.

In addition to maintaining chain 74 in a taut condition, the arrangement just described including spring 100 also provides an indication of the load which is being exerted on pusher 18 by the media in vat 10 as it, or the mechanical agitator where that is used, are moved through that media. As the load in front of the pusher increases the load on the drive mechanism will also increase, therefore tending to pull on chain 74, this pull will be such as to tend to rotate sprocket 94 in a counterclockwise direction and is thereby opposed by spring 100. However, movement of sprocket 94 due to this pull on chain 74 will produce movement of sprocket 94 and lever 98 and can be used as a control parameter. As illustrated, a limit switch 106 is associated with lever 98 and is connected in circuit with motor 86. When the movement of lever 98 is such as to indicate excessive loading on pusher 18, switch 106 will be operated to de-activate motor 86 thereby stopping the pusher. Where the vat is being emptied, the pusher being stopped the media in front of the pusher will tend to drain away gradually reducing the load on the drive mechanism so that it can subsequently be restarted. If necessary, a hand shoveling operation can be carried out to reduce the load in front of the pusher.

The remainder of the drive mechanism includes a basic control box 108 and an electric motor 1 10, pulley drive 112 and gear reducer 114, which provide the drive mechanism for the mechanical agitator where one is used.

Returning to FIG. 1, it will be noted that carriage 20 overhangs the side wall of track 22 as well as side wall 30. Since the track is offset from the center of the vat, this overhang is also provided to provide a support point for controls 116 which are readily accessible from the left side of vat 10 as viewed in FIG. 1.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. Apparatus of the type, described comprising, in combination,

a generally elongated vessel,

a generally elongated, horizontal extending track,

means supporting said track above said vessel and extending generally coextensively over said vessel,

a carriage,

a support arrangement for said carriage including three wheels engaging said track and connected to and supporting said carriage for movement along said track, in a horizontal sense said wheels being triangularly spaced,

said carriage having a portion extending laterally beyond one side of said track,

an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel,

first and second opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof,

and at least-one guide member connected to and movable with said carriage and positioned between and engaged by said opposed walls,

the spacing between said walls closely approximating the width of said guide member so that said guide member has a close fit between said walls.

2. The combination of claim 1 wherein said track is offset laterally to one side of the center of said vessel and said operative member is positioned on the center of the vessel.

3. The combination of claim 1 wherein said track is generally channel-shaped having a horizontal, generally planar bottom and upstanding side walls and one of said side walls forms said first wall,

and including a structural member attached to and projecting upwardly from said track bottom and providing said second wall.

4. The combination of claim 1 including an elongated element attached to and extending generally coextensively with said track,

and drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated.

5. The combination of claim 4 including means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition.

6. Apparatus of the type described comprising, in combination,

a generally elongated vessel having opposite ends,

a generally elongated, horizontally extending track, said track being generally channel-shaped and ex tending generally the length of said vessel, said track having a closed horizontal, generally planar bottom,

means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage,

a support arrangement for said carriage including three wheels engaging said track and connected to and supporting said carriage for movement along said track, in a horizontal sense said wheels being triangularly spaced,

said carriage having a portion extending laterally beyond one side of said track,

an operative member connected to said carriage portion'and extending into said vessel for movement through a medium contained in said vessel,

first and second generally elongated opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof,

and at least one guide member connected to and movable with said carriage and positioned between and engaged by said opposed walls,

the spacing between said walls closely approximating the width of said guide member so that said guide member has a close fit between said walls.

7. The combination of claim 6 including combination,

an elongated element attached to and extending generally coextensively with said track,

drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated,

and means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition.

8. The combination of claim 6 wherein the wheels of said three wheel support arrangement are arranged two on the side of said track over which Said carriage portion extends and the other on the opposite side of said track and between said two wheels relative to the longitudinal axis of said track,

and said guide member and elongated member are both located on the same side of said track and said elongated member is generally aligned with said guide member.

9. The combination of claim 8 wherein said elongated member is in the form of a chain and said driven element is in the form of a sprocket upon which said chain is engaged.

10. The combination of claim 8 wherein said track is offset laterally to one side of the longitudinal center of said vessel,

wherein said carriage extends over both sides of said track,

and including carriage control means connected to the portion of carriage extending over the side of said track opposite to that side over which the carriage portion to which said operative member is connected extends.

11. Apparatus of the combination,

a generally elongated vessel,

a generally elongated, horizontally extending track, means supporting said track above said vessel and extending generally coextensively over said vessel,

a carriage,

a support arrangement for said carriage including three wheels engaging said track and connected to and supporting said carriage for movement along type described comprising, in

said track, in a horizontal sense said wheels being triangularly spaced,

said carriage having a portion extending laterally beyond one side of said track,

an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel,

first and second opposed walls extending coexten sively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof,

and at least two guide wheels connected to and movable with said carriage and positioned between and engaged by said opposed walls,

the spacing between said walls closely approximating the diameter of said guide wheels so that said guide wheels have a close fit between said walls.

12. Apparatus of the type described comprising, in

a vessel, a track,

means supporting said track above said vessel and extending generally coextensively over said vessel,

a carriage,

a support arrangement engaging said track and connected to and supporting said carriage for movement along said track,

said carriage having a portion extending laterally be yond one side of said track,

an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel,

first and second opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof,

and guide means connected to and movable with said carriage and positioned between and engaged by said opposed walls,

the spacing between said walls closely approximating the width of said guide means so that said guide means has a close fit between said walls.

13. The combination of claim 12 wherein said track is generally channel-shaped having a bottom and upstanding side walls and one of said side walls forms said first wall,

and including a structural member attached to and projecting upwardly from said track bottom and providing said second wall.

14. The combination of claim 13 including an elongated element attached to and extending generally coextensively with said track,

drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated, and wherein said elongated element and guide means are arranged in general alignment.

15. The combination of claim 14 wherein said guide means is in the form of at least two wheels and the spacing between said walls closely approximates the diameter of said wheels.

16. Apparatus of the type described comprising, in combination,

a vessel,

a track,

means supporting said track above said vessel and extending generally coextensively over said vessel,

' a carriage,

a three wheel support arrangement engaging said track and connected to and supporting said carriage for movement along said track,

said carriage having a portion extending laterally beyond one side of said track,

and an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel,

an elongated element extending generally coextensively with said track,

drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated,

means connecting said elongated element to said track and including a spring member exerting a hiasing force on said elongated element to maintain said elongated element in a taut condition,

switch actuating means connected to and movable with said elongated element as said elongated element moves in response to variations in load on said operative member,

and switch means connected to and controlling said drive means and associated with said switch actuating means for operation thereby to de-activate said drive means when the load on said operative member exceeds a preselected limit.

17. Apparatus of the type described comprising, in

combination,

an elongated vessel having opposite ends,

an elongated, generally channel-shaped track extending generally the length of said vessel and having a closed bottom,

means supporting said track above said vessel and extending generally coextensively over said vessel,

a carriage,

a three wheel support arrangement engaging said track and connected to and supporting said carriage for movement along said track,

said carriage having a portion extending laterally beyond one side of said track,

an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel,

first and second generally elongated opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof,

at least one guide member connected to and movable with said carriage and positioned between said opposed walls,

the spacing between said walls closely approximating the width of said guide member so that said guide member has a close fit between said walls,

an elongated element extending generally coextensively with said track,

drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated,

means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition,

switch actuating means connected to and movable with said elongated element as said elongated element moves in response to variations in load on said operative member,

and switch means connected to and controlling said drive means and associated with said switch actuating means for operation thereby to de-activate said drive means when the load on said operative member exceeds a preselected limit.

18. Apparatus of the type described comprising, in

combination,

a vessel,

a track,

means supporting said track above said vessel and extending generally coextensively over said vessel,

a carriage,

means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition,

switch actuating means connected to and movable with said elongated element as said elongated element moves in response to variations in load on said operative member,

and switch means connected to and controlling said drive means and associated with said switch actuating means for operation thereby to de-activate said drive means when the load on said operative member exceeds a preselected limit. 

1. Apparatus of the type described comprising, in combination, a generally elongated vessel, a generally elongated, horizontal extending track, means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage, a support arrangement for said carriage including three wheels engaging said track and connected to and supporting said carriage for movement along said track, in a horizontal sense said wheels being triangularly spaced, said carriage having a portion extending laterally beyond one side of said track, an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel, first and second opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof, and at least one guide member connected to and movable with said carriage and positioned between and engaged by said opposed walls, the spacing between said walls closely approximating the width of said guide member so that said guide member has a close fit between said walls.
 2. The combination of claim 1 wherein said track is offset laterally to one side of the center of said vessel and said operative member is positioned on the center of the vessel.
 3. The combination of claim 1 wherein said track is generally channel-shaped having a horizontal, generally planar bottom and upstanding side walls and one of said side walls forms said first wall, and including a structural member attached to and projecting upwardly from said track bottom and providing said second wall.
 4. The combination of claim 1 including an elongated element attached to and extending generally coextensively with said track, and drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated.
 5. The combination of claim 4 including means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition.
 6. Apparatus of the type described comprising, in combination, a generally elongated vessel having opposite ends, a generally elongated, horizontally extending track, said track being generally channel-shaped and extending generally the length of said vessel, said track having a closed horizontal, generally planar bottom, means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage, a support arrangement for said carriage including three wheels engaging said track and connected to and supporting said carriage for movement along said track, in a horizontal sense said wheels being triangularly spaced, said carriage having a portion extending laterally beyond one side of said track, an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel, first and second generally elongated opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof, and at least one guide member connected to and movable with said carriage and positioned between and engaged by said opposed walls, the spacing between said walls closely approximating the width of said guide member so that said guide member has a close fit between said walls.
 7. The combination of claim 6 including an elongated element attached to and extending generally coextensively with said track, drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated, and means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition.
 8. The combination of claim 6 wherein the wheels of said three wheel support arrangement are arranged two on the side of said track over which said carriage portion extends and the other on the opposite side of said track and between said two wheels relative to the longitudinal axis of said track, and said guide member and elongated member are both located on the same side of said track and said elongated member is generally aligned with said guide member.
 9. The combination of claim 8 wherein said elongated member is in the form of a chain and said driven element is in the form of a sprocket upon which said chain is engaged.
 10. The combination of claim 8 wherein said track is offset laterally to one side of the longitudinal center of said vessel, wherein said carriage extends over both sides of said track, and including carriage control means connected to the portion of carriage extending over the side of said track opposite to that side over which the carriage portion to which said operative member is connected extends.
 11. Apparatus of the type described comprising, in combination, a generally elongated vessel, a generally elongated, horizontally extending track, means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage, a support arrangemenT for said carriage including three wheels engaging said track and connected to and supporting said carriage for movement along said track, in a horizontal sense said wheels being triangularly spaced, said carriage having a portion extending laterally beyond one side of said track, an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel, first and second opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof, and at least two guide wheels connected to and movable with said carriage and positioned between and engaged by said opposed walls, the spacing between said walls closely approximating the diameter of said guide wheels so that said guide wheels have a close fit between said walls.
 12. Apparatus of the type described comprising, in combination, a vessel, a track, means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage, a support arrangement engaging said track and connected to and supporting said carriage for movement along said track, said carriage having a portion extending laterally beyond one side of said track, an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel, first and second opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof, and guide means connected to and movable with said carriage and positioned between and engaged by said opposed walls, the spacing between said walls closely approximating the width of said guide means so that said guide means has a close fit between said walls.
 13. The combination of claim 12 wherein said track is generally channel-shaped having a bottom and upstanding side walls and one of said side walls forms said first wall, and including a structural member attached to and projecting upwardly from said track bottom and providing said second wall.
 14. The combination of claim 13 including an elongated element attached to and extending generally coextensively with said track, drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated, and wherein said elongated element and guide means are arranged in general alignment.
 15. The combination of claim 14 wherein said guide means is in the form of at least two wheels and the spacing between said walls closely approximates the diameter of said wheels.
 16. Apparatus of the type described comprising, in combination, a vessel, a track, means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage, a three wheel support arrangement engaging said track and connected to and supporting said carriage for movement along said track, said carriage having a portion extending laterally beyond one side of said track, and an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel, an elongated element extending generally coextensively with said track, drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated, means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition, switch actuating means connected to and movAble with said elongated element as said elongated element moves in response to variations in load on said operative member, and switch means connected to and controlling said drive means and associated with said switch actuating means for operation thereby to de-activate said drive means when the load on said operative member exceeds a preselected limit.
 17. Apparatus of the type described comprising, in combination, an elongated vessel having opposite ends, an elongated, generally channel-shaped track extending generally the length of said vessel and having a closed bottom, means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage, a three wheel support arrangement engaging said track and connected to and supporting said carriage for movement along said track, said carriage having a portion extending laterally beyond one side of said track, an operative member connected to said carriage portion and extending into said vessel for movement through a medium contained in said vessel, first and second generally elongated opposed walls extending coextensively with said track and having a preselected generally uniform spacing therebetween throughout the extension thereof, at least one guide member connected to and movable with said carriage and positioned between said opposed walls, the spacing between said walls closely approximating the width of said guide member so that said guide member has a close fit between said walls, an elongated element extending generally coextensively with said track, drive means in said carriage and including a driven element engaging said elongated element, said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated, means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition, switch actuating means connected to and movable with said elongated element as said elongated element moves in response to variations in load on said operative member, and switch means connected to and controlling said drive means and associated with said switch actuating means for operation thereby to de-activate said drive means when the load on said operative member exceeds a preselected limit.
 18. Apparatus of the type described comprising, in combination, a vessel, a track, means supporting said track above said vessel and extending generally coextensively over said vessel, a carriage, a support arrangement engaging said track and connected to and supporting said carriage for movement along said track, an operative member connected to said carriage and extending into said vessel for movement through a medium contained in said vessel, an elongated element and extending generally coextensively with said track, drive means in said carriage and including a driven element engaging said elongated element, said elongated element reeved on said driven element and said driven element operative to move along said elongated element and propel said carriage along said track when said drive means is activated, means connecting said elongated element to said track and including a spring member exerting a biasing force on said elongated element to maintain said elongated element in a taut condition, switch actuating means connected to and movable with said elongated element as said elongated element moves in response to variations in load on said operative member, and switch means connected to and controlling said drive means and associated with said switch actuating means for operation thereby to de-activate said drive means when the load on said operative member exceeds a preselected limit. 